Metal drawing process



Patented Oct. 14,1941

UNITED STATES PATENT OFFICE I 2,258,930. I 2

METAL DRAWING PROCESS Rudolf Haefner,'Frankfort-on-the-Main-Bomerstadt, and Max Scliunck, Oberursel, near Frankfort-on-the-Main, Germany No Drawing. Application January 21, 1939, Serial No. 252,208. In Germany January 25,

2 Claims.

work of drawing to put upon the tubes or body to be drawn before the drawing, a surface protecting layer, which prevents the directcontact of the tube or body and die, th'ereby'preventing. the deposition of metal in the hollow of the drawv plate. Ordinarily these protecting layers are of a metallic nature, and are produced by metallizing the pieces of metal to be worked by immersion in molten baths, or by immersion in metal salt solutions preferably accompanied by electrolysis, or by boilingprocesses. In theseways,

layers or coatings of lead, tin and copper, for

example, have been applied to the pieces of metal. Coatings of a non-metallic kind, which are ap plied in the formof apaint upon the pieces to be worked, are seldom used. With all of these,

undertaken in succession. For example,in drawing-hard steel, or when many successive draws without intermediate treatment are .to be performed, bitumens with a softening point between 60 and 100 Celsius are chosen, while in drawing softer metals, such as iron, bitumens with a'softening point below 60 Celsius are employed advantageously.

The manner of applying the bitumen to the surfaces of the metal pieces to be drawn is as follows: the'solid bitumen is dissolved in a suitable solvent, for example, benzine, and the pieces of metal are then treated with the solution by and fats, for example, parafiin oil. The following are' given as examples of coating .composi coatings it is necessary inconjunction with the drawing process to use a' drawing fat or drawing oil, in order to reduce the friction in the dies.

The present invention'relates to a non-metallic coating medium, and to process for drawing metal, which prevents deposit in* the dies, which simultaneously eflects lubrication, which does not require the addition or use of drawing fat and the like, which is extremely'simple to use or operate and which, at the same time, is comparatively inexpensive.

sides in that the coatings according tothe presnet invention, after having beenpreliminarlly applied to the metal to be drawn,.are able thereafter to bear or experience. several successive drawing operations of the metal without it be- A particular and surrising advantage of the present invention recoming again necessary,. between the separate 7 or individualidrawings to treatathe surface of the metal to be drawn. For example, iron tubing of 2.5- mm. wall thickness, after having been coated according to the present invention, is able to be drawn-or stretched in three successive drawing operations, without intermediate annealing, to a wall thickness of 1.0 mm. and with-v out it being or becoming necessary to repeat the treatment of the metal with the drawing composition according to the invention. 7 I

The invention utilizes pure bitumen, for example petroleum bitumen. Such form of .bitumen, of course, has not been h ted with sulphur tosulphurize it. The solte v point of the bitumens to be used according tothe present invention can be chosen between 20 and 100 Celsius according to the metal to be drawn and the degree of cross section reduction or the number of drawing operations or pulls which are to be dipping them in the solution or coating the solution upon them. After evaporation of the solvent, the actual drawing of metal pieces can then be performed in a suitable known manner.

Especially good results are also obtained when .bitumens of high softening point are employed if their softening points have been lowered by p the addition of mineral, vegetable or animal oils tions suitable for use according to the present invention:

. Kilograms (1) Petroleum bitumen of C. softening point 50 -Benzine 50 (2) Petroleum bitumen of C. softening point 4 Paraflin nil 5 Benzin I 45 We claim:

.1. The process which comprises applying to metal to be drawn a' coating composition comprising a soliitionpf a non-sulphurized bitumen of 20 to- Celsius softening point in about an equal weight of a volatile solvent for the bitumen, and after evaporation of volatile solvent from the said applied composition, subjecting the so treatedmetal toa drawing operation.

2. The process which comprises applying to metal to be drawn a coating composition comprising a solution, ina volatile solvent of a solid non-sulphurized bitumen and a material which lowers the softening point of the bitumen, a

.hundred parts by weight of said solution con taining about fifty parts byweight of the bitumen, a few parts by weight of'the material which lowers the softening point of the bitumen anda few partsless than fifty parts by weight of the volatile solvent; and after evaporation of the volatile solvent from the applied compositiOn; subjecting the so treated metal to a drawing operation.

RUDOLI" HAEFNER. ax scrmNcK. 

